OBJECTIVES: To continue program of measurements of the enthalpies of solutions of non-reactive gases in liquids including water and water containing solutions. Also to continue measurement and interpretation of solvent isotope effects on the properties of solutions, particularly aqueous solutions and solutions exhibiting the phenomenon of hydrophobic bonding. METHODS: The techniques employed will include isothermal gas-liquid calorimetry, differential capacitance manometry, vibrating tube densitometry, and other standard methods for the measurement of partial molal free energies, enthalpies and volumes of solutions. We have extensive experience with all of these techniques.